Sizing

Pediatric sizing

You do not size a child by age. You size by four numbers, then pick hardware that matches weight.

Charts are manufacturer ranges for shopping, not a prescription. A CPO measures. Sample GrowPin S/M shells are two points on this map, not a complete size run.

Four measurements

Distal circumference

Tape on skin, 4 cm up from the end, medium tension. That number in cm is the Iceross size (Junior 12 / 14 / 16 / 18).

Residual length

Bone end to the next joint crease (knee or elbow). Kids add about 1–2 cm per year if the growth plate is intact.

Sound-side foot or palm

Heel-to-toe in cm = prosthetic foot size. Palm width at MCP heads = printed hand scale.

Body weight

This picks the pylon. Pediatric 22 mm aluminum to 35–45 kg. Adult 30 mm after that. Never mix.

GrowPin S and M

Inner collet, approximate. The BOA/cord covers one circumference jump. Then reprint the liner, keep the frame.

Shell	Inner circ. (approx)	Typical age	Matches
Hand S	≈ 9–11 cm distal	2–5	Palm ~55 mm. Toddler transradial.
Hand M	≈ 12–14 cm distal	5–9	Palm ~65–75 mm. Electrohand 2000 size 5–6 territory.
Leg S	≈ 22–24 cm mid-socket	4–8	Junior liner 12–16. 22 mm pylon. Foot 14–18 cm. <35 kg.
Leg M	≈ 26–28 cm mid-socket	8–12	Junior 16–18 or small adult. Still 22 mm until 45 kg.

Feet — buy to the sound shoe

Ottobock pediatric feet are sold in centimetres of foot length, not US shoe size. Max weight is the hard stop, not age.

Foot (cm)	≈ US kids	≈ age	Catalog	Max kg
12–13	4–6 toddler	1–2	1S30 SACH child	35
14–15	7–9 toddler	2–4	1K10 dynamic	45
16–17	10–12 little kid	4–6	1K10	45
18–19	13 – 1 youth	6–8	1K10	45
20–21	2–3 youth	8–10	1K10, last pediatric	45
22+	4 youth / adult	10+	Adult foot + 30 mm	by foot

Liners

Iceross Junior locking: 12 / 14 / 16 / 18 cm. Sizes 12–14 use an M6 pin. Then you jump to adult Iceross (25+).

Measure 4 cm proximal to the distal end, on skin, limb hanging.
If between sizes, the smaller liner is usually safer (less stretch, less pistoning).
Replace every 6 months on a growing child. ~$300. This is the real annual cost.

Hands

Passive from ~6 months. Body-powered around 3. Ottobock Electric Hand 2000: sizes 5 / 5½ / 6 / 6½ (~85–130 g). Shop lists size 6 for ages 5–10, 6½ for 8–13.

e-NABLE / Cyborg Beast: scale to sound palm width, not age. ~4.5 cm toddler → ~7 cm teen.
GrowPin terminal is a silhouette, not a gripper. Size the gauntlet to residual circumference.

How often they outgrow it

AAPM&R whole-prosthesis replacement is slower than socket tightness. Your 5–6 month instinct is the inner, not the foot.

Age	TPU inner	Frame	Foot / terminal	Whole limb (clinic)
0–5	Every 4–6 mo	Yearly	With shoe size (~3–6 mo)	Yearly
5–12	Every 6–8 mo	Every 1–2 yr	Every 6–12 mo	Every 2 yr
12–16	Yearly	Until weight jumps pylon	As shoes jump	Every 5 yr

Residual length grows ~1–2 cm/year when the physis is preserved. Distal pads on the GrowPin liner cover ~13 mm — about one school year. Bony overgrowth (terminal spike) happens in a large fraction of kids amputated before 12; that is a surgeon problem, not a bigger socket.